@incollection{MEM_2023_52_a7,
     author = {Manev, Mancho},
     title = {Preface},
     booktitle = {},
     series = {Mathematics and Education in Mathematics},
     pages = {5--6},
     year = {2023},
     volume = {52},
     language = {bg},
     url = {http://geodesic.mathdoc.fr/item/MEM_2023_52_a7/}
}